What exactly are you basing belief in the existence of this possibility in the DV on ?
#1. She doesn't seem the type for self sacrifice. Haven't seen any redeeming quality from her the entire series.
#2. Nicodemus believes God will lose, making me believe he has an idea or plan on why he'll lose.
#3. Nicodemus stored her soul in a place where their "enemy" can't get it which makes me believe he cannot gain access to hell, but he can return to Hades realm.
#4. His plan was to obtain many powerful holy relics which uses are unknown but considering that a powerful being who's blood touched them rose from the dead gives reason to believe that they may have the power to raise someone else.
#5. There is a girl within the series who has been in a coma, and therefor her importance for the story could be her body being used as a vessel. If she serves no importance, why have her in the story at all?
#6. Hades is not the power he once was. Souls are stored in his realm but he does appear to be a being that can make deals, or be simply overpowered, meaning the souls are not in some unbreakable vault.